The subject invention concerns a shoe sole having a biodynamically shock-absorbing structure. The shoe sole is particularly suitable for sports shoes and may be used for instance for jogging and running on hard surfaces, such as asphalt. It may also be used in walking boots and similar footgear.
In walking and running the foot has to bear considerable weight when it is set down into contact with the ground or the surface underneath. The cushion of fat found for instance in the heel dampens the impact upon heel strikes, that is the phase of the walking cycle when the heel is set down into contact with the surface underfoot. At the midstance stage of the walking cycle, when the whole foot is in contact with the surface, and at the heel elevation stage, the weight is on the lengthwise arch of the foot and on the forward transverse arch of the foot, which may cause deformation of these arches.
Congenital anatomic conditions or weaknesses may impair or weaken these functions and may cause insufficiency problems, which originate from the arches of the foot. The problems caused by weakened arches may be remedied by arch supports which are positioned inside the shoe. Also originally normal arches may, when exposed repeatedly to heavy weights on account of walking and running on very hard surfaces, lose their vaulted shape and consequently their weight-distributing capacity, which could also produce insufficiency symptoms.
This type of problems are common and are primarily caused by the use of bad shoes or e.g. by activities on hard surfaces, such as asphalt and concrete. Preventive as well as therapeutic measures to avoid such insufficiency conditions therefore are very important. Mal-functioning of the feet and absorbing shoes that are badly constructed may also cause damage and lead to insufficiency conditions, particularly in the lower extremities, such as the ankle joint, the menisci, knees, hips and the back.
Sport activities also expose the body to considerable stress and strain. In sports such as running, various kinds of jumping and the like it is particularly during the heel strike stage that considerable weight has to be borne by large portions of the skeleton, which may cause damage to the knee, back or other exposed parts of the body. These damages may occur as a result of long-standing and repeated weight bearing, as is the case with for instance long-distance runners, or may be caused by isolated instances of heavy but unsuitable exposures to weight bearing, such as may be experienced e.g. in triple jumping. Shoes for sports used therefore should have a sole which is able to cushion as far as possible the shocks that arise from the setting down of the foot on the ground. However, the sole must not be too thick, as this would make the shoe too heavy and thus impair the achievable results of the contestant.
Different kinds of sole constructions are available, designed to provide a shoe that obviates the drawbacks outlined in the afore-going. For instance, on the market there are shoes having soles comprising several layers of different materials to provide the desired resiliency. Soles are available that incorporate an air-cushion positioned underneath the heel to provide maximum shock-absorbing properties. Shoes equipped with soles of this kind have a good overall shock-absorbing capacity.